For the Layperson: A Simple Guide to Image Prep for the Web

Est. Reading Time: 4 minutes

With the development of user-friendly Content Management Systems, we now see many people using these tools to edit their own websites. Often times, this includes adding images to your page, and almost always you will want to work within a certain image size constraint so that the images will fit better into the layout of your site. Here are some simple guidelines to follow to ensure that your images are appropriate for the web and a easy tutorial on how to crop images to a specific size using Photoshop.

Have an image you want to use on the web? Check it’s size. If you are trying to use an image for a header banner graphic that spans the entire width (or close to it) of the website you will probably need more than 500 pixels. In Photoshop the easiest way to do this is to go to Image > Image Size and check there. No matter what the resolution is set at in this box, the number of pixels in an image stays the same (unless you modify the size while in this box). For web, 72 pixels/inch is always used but even if your image is currently set at a resolution of 300 pixels/inch the Width and Height under Pixel Dimensions will stay the same so you can at least know this and see if you have enough pixels in your image for the spot on your website you want to use the image for.

The absolute easiest way to crop an image and get it pixel perfect height and width is to use the crop tool in Photoshop. With your image open, select the crop tool from the tool panel (of you can use Ctrl+C on your keyboard). Once the tool is selected you will notice you have Crop Tool specific settings in the top bar. This is where the magic happens. If you know you have to create and image that is exactly 200 pixels by 300 pixels you can enter this in the bar. Just use “px” after your size to denote that you want to crop to pixels (as opposed to inches or centimeters) and make sure that your resolution is set to 72 pixels/inch (also called dpi). 72 dpi is the image resolution that is always used for the web because this is the standard resolution for computer screens.

Once you have the appropriate values entered in, all you have to do is click and drag your crop tool over your image to select the portion of the image you would like to crop and resize, then just double-click to finalize. One thing to keep in mind is watch the clarity of your image. If after make your cropping and the image seems to “pixelate” (it will zoom in a bit and get fuzzy) this means that your image was smaller than the size you chose to crop to and you have lost image quality. You may want to crop differently if possible, or use another image.

Once you are content with your selection the best way to save an image is to go to File > Save for Web and Devices. A box will pop up that will allow you to select what file format you want to use and how much you want it to compress the image (this will make the file size smaller to allow for quicker loading times). My go-to is usually a .JPG with a image quality of about 70. This will make the image a bit smaller without sacrificing quality. For larger images you may want to go a bit lower, but keep an eye on the image quality. If my image is already a bit low-quality I will save it with a quality of 100. I only use .PNG if parts of my image are transparent and .GIF is used for flat color graphics that need to be a small file size. Using .GIF for many images will mean a large sacrifice in quality. The preview window will show you exactly what your image will look like when it is output. This will help you double check image size and file size in advance, so take advantage of it. It’s better to consider things now rather than put your image up on your site only to notice then that it is the wrong size or has an issue with the image quality.

Hopefully this guide will give you a few tips or help you understand the tools a bit better if you are trying to prepare images for your site or even just check the sizing of images for you pass them on to someone else to use for a specific purpose.